Encourages JS to publish on sterility of orchids and to experiment on Passiflora.

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Doubted Hooker's poppy case.

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Describes case of primrose with three pistils: when pulled apart allowed pollen to be placed directly on ovules. This supports JS's explanation of H. Crüger's case.

Transcription

Down Bromley Kent

Ap. 12th

My dear Sir

I really hardly know how to thank you enough for your very interesting letter. I shall certainly use all the facts which you have given
me (in a condensed form) on the sterility of orchids in the work which I am
now slowly preparing for publication.— But why do
you not publish these facts in a separate little paper? they seem to me well
worth it, & you really ought to get your name known. I
could equally well use them in my Book. I earnestly hope that you will experiment on
Passiflora, & let me give your results.

Dr. A. Grays observations were made loosely, he said in letter
he would attend this summer further to the case, which clearly
surprised him much.— I will say nothing about the
Rostellum, stigmatic utriculi, fertility of Acropera & Catasetum, for I am
completely bewildered:it will rest with you to settle thesepoints by your excellent observations & experiments.— I must
own I never could help doubting Dr. Hooker's case of the
Poppy.— You may like to hear what I have seen this
morning: I found a Primrose plant with flowers having 3 pistils,
which when pulled asunder without any tearing, allowed pollen to be placed on ovules.
This I did with 3 flowers— pollen tubes did not protrude after
several days. But this day, the sixteenth (N.B Primulas seem naturally slowly
fertilised) I found many tubes protruded, & what is very odd they certainly
seemed to have penetrated the coats of the ovules, but in no one instance the
foramen of the ovule!! I mention this because it directly
bears on your explanation of Dr. Cruger's case.— I believe that your explanation is right; I
shd. never have thought of it; yet this was stupid of me, for
I remember thinking that the almost closed imperfect flowers of
Viola & Oxalis were related to the protrusion of the pollen-tubes. My case of the Aceras with aborted labellum squeezed
against stigma supports your view.—
Dr. Cruger's notion about the ants was a simple
conjecture.— About crptogamic filaments rember
Dr. C. says that the unopened flowers habitually
set fruit—

I think that you will change your view on the imperfect flowers of Viola &
Oxalis; I am now making a few observations on them: last
year I observed a few intermediate forms.—

I have asked everywhere for seed of Campanula perfoliata.
Can you get me any?

I am particularly obliged for your remark on Auriculas.—

It seems to me a good experiment, that of preventing the orchid flowers
opening.— What an excellent &
indefatigable observer you are.

with sincere respect | Yours very faithfully | Ch. Darwin

P.S. Mr. Anderson sent me some seeds of the ``abortive''
Cattleya crispa; & not one in 100 or 200 contained even a
trace of nucleus; the testa being quite empty.—

The year is established by the relationship between this letter and the letter from
John Scott, [1--11] April [1863].

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f2 4084.f2

Letter from John Scott, [1--11] April [1863].

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f3 4084.f3

CD wrote a draft of the section of Variation on `Crossing &
Sterility' between 1 April and 16 June 1863
(Variation 2: 85--191; see `Journal' (Correspondence vol. 11,
Appendix II)). Scott's observations on self-sterility and cross-fertility in
Oncidium and Maxillaria were briefly discussed in Variation
2: 133, 164.

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f4 4084.f4

Scott detailed his observations on self-sterility and cross-fertilisation in the
orchid genus Oncidium in a paper read before the Botanical Society of Edinburgh
on 14 May 1863 (Scott 1863a). See also Scott 1864b.

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f5 4084.f5

CD had been encouraging Scott to experiment on Passiflora since
March 1863 (see letter to John Scott, 24 March [1863] and
nn. 3 and 4). Scott later published his experiments on
Passiflora in Scott 1864d. CD referred to Scott's results in
Variation 2: 137--8. See also Cross and self fertilisation,
p. 330.

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f6 4084.f6

CD refers to Asa Gray's observations of pollination in Gymnadenia
tridentata, made in July and August 1862 (see Correspondence
vol. 10, letters from Asa Gray, 29 July 1862 and
18--19 August 1862), and to the letter from Asa Gray,
22 September 1862 (ibid.). See letter from John Scott,
[1--11] April [1863] and n. 13.

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f7 4084.f7

See letter from John Scott, [1--11] April [1863] and nn. 16--17. CD
subsequently discussed Acropera and Catasetum in `Fertilization of
orchids', pp. 153--4 (Collected papers 2: 150--1); see also
Orchids 2d ed., pp. 247--57, for mention of these genera, and for
further discussion of the rostellum.

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f8 4084.f8

The reference is to an article by Joseph Dalton Hooker on the possibility of
artificially pollinating flowers of the blue poppy without the involvement of the stigma
(J. D. Hooker 1854a). See letter from John Scott, [1--11]
April 1863 and n. 19.

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f9 4084.f9

See letter to Daniel Oliver, [12 April 1863] and n. 3,
letter from Daniel Oliver, 14 April 1863, and letter to Daniel Oliver,
[after 14 April 1863].

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f10 4084.f10

See letter from John Scott, [1--11] April [1863] and n. 25. Hermann
Cr¨uger had observed the emission of pollen-tubes while the pollinia remained
in situ in unopened flowers of Epidendreae (see letter from Hermann
Cr¨uger, 23 February 1863).

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f11 4084.f11

See letter from John Scott, [1--11] April [1863] and n. 30.

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f12 4084.f12

In Orchids, p. 324 n., CD described `monstrous' flowers
of Aceras in which pollen germinated and formed pollen tubes while still in the
anther. See also letter to John Scott, 24 March [1863], and letter from John
Scott, [1--11] April [1863].

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f13 4084.f13

See letter from John Scott, [1--11] April [1863]. In his letter to CD of
23 February 1863, Cr¨uger had suggested that the protrusion
of pollen-tubes that he had observed in Epidendreae (see n. 10, above) was due
to ants carrying stigmatic fluid to the pollen. See also letter to John Scott,
24 March [1863].

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f14 4084.f14

Scott had suggested (see letter from John Scott, [1--11] April [1863]) that the
pollen-tubes described by Cr¨uger as occurring in unopened orchid flowers
(see letter to Journal of Horticulture, [17--24 March 1863])
could be fungal filaments; Scott had observed such filaments in the flowers of
Bletia, initially mistaking them for pollen-tubes.

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f15 4084.f15

As he explained in his letter of [1--11] April [1863], Scott believed that the
germination of pollen-grains in situ in cleistogamic flowers, like those of the
imperfect forms of Viola and Oxalis, was a `purely accidental
occurrence, having no ultimate import in the economy <of> the
spec<ies>'. For CD's study of the flowers, see n. 16, below, and
letter to Journal of Horticulture, [17--24 March 1863] and
n. 7. See also letter to Asa Gray, 31 May [1863].

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f16 4084.f16

For CD's observations of Viola and Oxalis in March and
April 1863, see DAR 111: 6, 10, and 45. For CD's observations and experiments
on the two genera in 1862, see Correspondence vol. 10. CD's published
observations on cleistogamic flowers in these genera are in Forms of flowers,
pp. 314--24.

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f17 4084.f17

See letter to Asa Gray, 20 March [1863] and n. 5. For CD's notes
on the genus, see DAR 111: 29--32.

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f18 4084.f18

Scott had forwarded information to CD regarding the inheritance of style length in
Primula auricula (see letter from John Scott, [1--11] April [1863]).

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f19 4084.f19

To investigate the cause of self-fertilisation in flowers that did not open, Scott
had suggested cementing together the perianths of `perfect' flowers shortly before their
expansion (see letter from John Scott, [1--11] April [1863]).